New (to me) chickens - 1/3 egg shell in nest

Hmmmm....I'm a little concerned. I got 4 hens on Wednesday from a friend of my dad's (barred rock, columbian rock, rir, silkie). They are all somewhere around a year old. The first night we got a beautiful egg, the next day another (they were different colours and I assumed from 2 different birds). The 3 standards were laying well before they came here and I don't know about the silkie.

There was nothing in the nest box at 8am this morning and I checked again at noon and all that was there was about 1/3 of a shell and membrane but that was it. Nothing else in the box or the rest of the coop and no evidence of anything else. The shell does feel soft and it's kind of crushed but stuck to the membrane.

Do you think that's all that came out??? A transition thing because the place and routine changed?? OR - do you think they ATE IT?!

It's a bad habit for them to get into. Do a search on this forum for more info.; some folks put golf balls into the nest boxes to discourage them from eating eggs (they try to eat them and when they can't crack the "shell" of the golf ball, they give up) or even goose eggs, because the shells are harder. Best to nip it in the bud.

Hmmmm....well, I wouldn't think they are overcrowded. They have 12 sq feet of space for 3 standards and 1 bantam, with 2 4' roosts, one high up in the roof. Nutritionally they are getting crumbed layer feed, oyster shell and grit. These standards came from a caged egg-laying situation so they've not really had access to a nest or their own eggs before. Curiousity??